page_title: Boeing 737 MAX certification
section_title: Boeing 737 safety analysis
hierarchical_section_title: Boeing 737 MAX certification / Boeing 737 safety analysis
caption_attribution_description: English: Probability vs consequence graph, perexcerpt from FAA AC 25.1309-1A
context_page_description: The Boeing 737 MAX gained its type certification from the FAA and EASA in March 2017. Boeing had worked to ensure the aircraft retains a compatible type rating with all other aircraft in the 737 family, thus avoiding costly simulator training and the need to learn about new systems. Within two years, the aircraft was involved in two fatal accidents, Lion Air Flight 610 and Ethiopian Airlines Flight 302, and grounded worldwide in March 2019.
  On March 11, 2019, a U.S. federal grand jury issued a subpoena on behalf of the U.S. Justice Department for documents related to development of the 737 MAX. On March 19, 2019, the U.S. Department of Transportation requested the Office of Inspector General to conduct an audit on the 737 MAX certification process. Over the next several months, The Seattle Times's award-winning coverage of the ongoing crisis revealed how management decisions at Boeing and the FAA pushed for cost-saving solutions, but ultimately produced a flawed design with insufficient oversight.
context_section_description: Recognized civil aviation development practices, such as those of SAE International ARP4754 and ARP4761, require a safety process with quantitative assessments of availability, reliability, and integrity, validation of requirements, and verification of implementation. Such processes rely on engineering judgment and the application of these practices varies within the industry. Redundancy is a technique that may be used to achieve the quantitative safety requirements.
  Aviation safety risk is defined in AC 25.1309-1, an FAA document describing acceptable means for showing compliance with the airworthiness requirements of § 25.1309 of the Federal Aviation Regulations (FAR). A catastrophic failure must have an extremely improbable rate, defined as one in a billion flight hours, also stated as less than 10⁻⁹ per flight hour.
  By this measure, as of 2005, the Boeing 737 had an actual fatal accident rate of 1 in 80 million flight hours, missing the requirements by an order of magnitude.
  In the two years of the 737 MAX's commercial service prior to its grounding, the global fleet of nearly 400 aircraft flew 500,000 flights and suffered two hull loss incidents. As of March 11, 2019, the 737 MAX's accident rate was second behind the Concorde, with four accidents per million flights, compared to the 737NG 0.2 accidents per million flights.
caption: AC 25.1309-1A fig 1 Probability vs consequence graph. This chart defines acceptable risk and unacceptable risk.
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